Study on anomalous low temperature aging and strengthening of gold-titanium based superelastic alloys exhibiting high biocompatibility and X-ray radiography for practical applications

2015 Fiscal Year Final Research Report

• Project/Area Number: 26630343
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Structural/Functional materials
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Hosoda Hideki 東京工業大学, 精密工学研究所, 教授 (10251620)
• Co-Investigator(Kenkyū-buntansha): INAMURA Tomonari 東京工業大学, 精密工学研究所, 准教授 (60361771) ; TAHARA Masaki 東京工業大学, 精密工学研究所, 助教 (80610146)
• Project Period (FY): 2014-04-01 – 2016-03-31
• Keywords: 低温時効 / ナノ構造変化 / 微細組織 / 平衡相 / 非化学量論組成 / 機械的性質 / 金合金

Outline of Final Research Achievements

Au-Ti binary and Co added ternary and quaternary alloy systems were used in this study. Several trials were done to fabricate single crystals using OFZ method, but no single crystal was obtained. Probably, some complex phase reactions containing peritectic reaction is related to solidification. Then, instead of single crystal, we used polycrystal alloys for further researches. It was found that Ti-rich offstoichiometric alloys exhibit good mechanical properties, and that aging behavior is not observed in Au-Ti binary alloys but Co-added alloys only. The equilibrium second phase is A15 AuTi3 in the binary system but it is changed to be L12 phase by Co addition. By TEM observations the size of this precipitates is relatively large from sub nm to a few microns, and no clear microstructural change is recognized such as APB and vacancy cluster. Then, the anomalous low temperature aging must be due to the L12 precipitates stabilized by Co addition.

Free Research Field

材料工学